Below are the contracts that must appear in public or private documents for the purpose of making them EFFECTIVE AGAINST THIRD PERSONS but not for the purpose of validity of the contract:

1. Sales contracts
Sale of real property or of an interest therein must appear in a public instrument. (Arts. 1358 and 1403, No. 2(e), Civil Code) When the sale is through an agent, the authority of the latter must be in writing; otherwise the sale shall be void. (Art. 1874, Civil Code) A letter containing the authority to sell is held sufficient; it need not appear in a public instrument. (Gregorio Jimenez v. Pedro Rabot, et al., G.R. No. 12579, 27 July 1918).

Sale of goods, chattels or things in action, at a price not less than Five hundred pesos, must be in writing, unless there is partial delivery or partial payment. (Art. 1403, No. 2(d), Civil Code)

2. Land lease agreements
Lease of real property or of an interest therein for a longer period than one year must be in writing. (Art. 1403, No. 2(e), Civil Code)

3. Credit Transactions

A real estate mortgage must be recorded in the Registry of Property. “If the instrument is not recorded, the mortgage is nevertheless binding between the parties.” (Art. 2125,par. 1, Civil Code)

A chattel mortgage must be registered in the Chattel Mortgage Register for the validity of the contract. (Art. 2140, Civil Code)

A contract of guaranty and of suretyship must be in writing since they are special promise to answer for the debt, default, or miscarriage of another. (Art. 1403, No. 2(b), Civil Code)

A contract of pledge shall not take effect against third persons if a description of the thing pledged and the date of the pledge do not appear in a public instrument. (Art. 2096, Civil Code) It is necessary in order to constitute the contract of pledge that the thing be placed in the possession of the creditor, or of a third person by common agreement. (Art. 2093, Civil Code)

B. Below are the contracts that must appear be in writing or must be registered for the purpose of VALIDITY of the contract:

1. Credit Transactions

A chattel mortgage must be registered in the Chattel Mortgage Register for the validity of the contract. (Art. 2140, Civil Code). An affidavit of good faith must be appended to the mortgage and recorded therewith. [Sec. 5, Act No. 1508 (The Chattel Mortgage Law)]

In the contract of antichresis, “the amount of the principal and of the interest shall be specified in writing; otherwise the contract of antichresis shall be void.” (Art. 2134, Civil Code)

“No interest shall be due unless it has been expressly stipulated in writing.” (Art. 1956, Civil Code.)

2. Other contracts

“All other contracts, where the amount involved exceeds five hundred pesos must appear in writing, even a private one.” (Art. 1358, par. 2, Civil Code)